1. Field of the Invention
This invention relates in general to certain new and useful improvements in an apparatus and the method for making an improved wide angle light diffusing lens and more particularly, to an apparatus and method of the type stated which permits a molding of the lens in a unique manner to produce wide angled light dispersion with the resultant lens.
2. Brief Description of the Prior Art
In the aforesaid co-pending application, there is described a unique and novel light diffusing lens of the type which is adapted for disposition across a downwardly facing opening of an overhead light. This light diffusing lens is a vast improvement over the conventional light diffusing lenses or so-called "defusers" and which prior art lenses each generally comprises a relatively rigid flat sheet of a plastic, material such as an acrylic plastic. These lenses usually have dimpled or prismatic elements on the surfaces of the lens. Nevertheless, because these prior art lenses are relatively flat sheets with light dispersal at an angle of 45 degrees from the edges, direct light distribution is relatively limited to areas beneath the lens.
Heretofore, it was assumed that in order to adequately light a work station or other area in which optimum lighting is desired, that all of the light from a fixture or at least a substantial portion of light from a fixture should be directed downwardly to that work station or other area where light is desired. In short, no effort was made to direct light to upper portions of side walls of a room or to a ceiling of a room. As a result, the only lighting on the upper portions of a room side wall or ceiling was a result of reflected light.
Most prior art light fixtures and the diffusing lenses used therewith were designed to provide light dispersal from the edges of the lens at an angle of about 45 degrees. Thus, the two opposite sides of a lens, actually provided light dispersion over a 90 degree angle on each of the sides of the lens. In some cases, the light dispersion did occur at about 65 degrees from planes at each of the vertical edges of the lens. However, in the prior art the maximum effective light dispersion was about 130 degrees. This also resulted in poorly lighted upper wall areas and ceilings of a room. One of the problems associated with the prior art lens was the harsh light condition. Inasmuch as the prior art lens was generally a relatively flat planar sheet, the sheet itself was very closely spaced from the actual light source, such as the fluorescent lamp or lamps. As a result, harsh light was generated. There were attempts to obviate this problem because of the resultant glare in glass surfaces, computer screens and the like, although these attempts to reduce the glare either reduced the amount of light or had other serious side disadvantages.
In the aforesaid co-pending patent application, there is described a lens which has a vertically positioned peripherally extending wall. Extending inwardly and downwardly from two of the longitudinal edges of that generally vertically arranged wall are a pair of side walls. Moreover, downwardly and inwardly extending end walls connect to the side walls and all meet at a joined line forming a lowermost edge of the lens. In accordance with this construction, light was defused from the vertically positioned peripheral wall as well as the inwardly and downwardly converging side walls and the end walls. As a result, there was a very wide dispersion of light substantially across all portions of a room, including upper portions of the walls and the ceilings of the room.
In most prior art lighting systems, it was generally assumed, as aforesaid, that light should be directed downwardly with little or no attempt to light upper portions of a room. It has been found in connection with the light diffusing lens in the co-pending patent application that personnel using a particular room believed that there was more light available at a given work station, when all portions of the room were well lighted with substantially equal light distribution across all portions of that room, when there was no given increase in light output compared to a conventional prior art lenses. In other words, the well-lighted effect of all portions of the room led the users or occupants of the room to believe that lighting output had been increased. Further, as a result of the fully lighted room, the lens of the aforementioned co-pending patent application provided an improved psychological effect on the occupants of the room where there is an even and substantially wide light distribution.
One of the main problems encountered with the aforesaid light diffusing lens was the need for a suitable apparatus and method to produce this lens. In achieving the wide angled light distribution, it was found that by distorting the effect of the prisms and the aligned rows of prisms on the surface of the lens, that an irregular but more highly diffused light pattern was achieved. It was therefore necessary to find a way to obtain this irregular surface effect without completely distorting an original sheet of plastic and maintaining properties necessary for durability of the plastic and without overheating or burning the plastic sheet during forming thereof.
The prior art lens producing techniques did not lend themselves to production of a light diffusing lens of the type required. Generally, all prior art apparatus and method for producing relatively flat sheet lenses relied upon a simple extrusion process. Even if any molding was involved, the molding operation was simple and was adapted to generally produce a flat sheet of an acrylic plastic. If the plastic sheet was provided with a dimpled surface, or otherwise a prismatic surface, the process was such that the dimples or prisms were all of a regular shape and in regular rows and columns and at least formed in a regular pattern on the surface of the sheet. Consequently, prior art techniques for producing a lens were not acceptable for use in producing the wide angle light diffusing lens of the type taught in the aforesaid co-pending patent application.